Toothed-gear coupling



April 24, 1945. K. Bl GILLMORE ETAL 2,374,344

TOOTHED GEAR COUPLING Filed Aug. 2l, 1.943

Patented Apr. 24, 1945 TOOTHED'- GEAR COUPLING Kenneth Bryan Gillmore,London, and Robert Henry Warde, Hatfield, England, assignors to TheDe'Havilland Aircraft Company Limited,

Hatfield, England Application August 21; 1943, Serial No. 499,590 InGreat Britain September 30, 1942 Claims.

The present invention consists in a toothedgear coupling, in which atleast one of the co-` operating toothed gears, whilst beingnon-rotatably mounted on its driving member for positive transmission ofdriving torque, includes means resiliently loading it towards thecooperating toothed member.

The invention has a particular application in airscrew pitch-changingmechanism which includes a toothed driving bevel through which thepitch-changing movement is transmitted to the individual airscrew bladesunder control of a driving bevel cooperating with driven bevels carriedby or drivably coupled to the individual blade roots. In sucharrangements the resilient loading may be incorporated as between thepitchchange driving bevel and the shaft, sleeve, or equivalent memberwhich mounts it, the resilient loading operating to urge the bevel intoengagement with the cooperating driven bevels transmitting pitch-changedrive to the blades. In that case the resilient loading can convenientlyoperate in an axial sense, driving torque being transmitted throughsplines permitting axial displacement of the pitch-change driving bevelrelative to the shaft or sleeve which mounts it, such splines at thesame time serving to ensure rotation of the bevel in a xed relation toits shaft or sleeve. In cases where the driven bevels on the individualblades are resiliently loaded in the sense according to the presentinvention, the efi ect of the resilience will necessarily be such thatthe driven bevels are urged radially towards the pitch-change drivingbevel, although the loading may exert an influence which is acombination of axial and radial loading. In some cases both the drivingand driven bevels may include resilient loading means.

In order that it may be clearly understood and readily carried intoeect, the invention is hereinafter described with reference to theaccompanying diagrammatic drawing, of which:

Figure l is a plan view illustrating the invention as applied in theresilient loading of a driven pitch-change bevel to urge it laterallyinto engagement with a driving bevel which is rigidly mounted.

Figure 2 is a view similar to Figure l but illustrates a slightlymodified arrangement.

Referring first to Figure 1, pitch-change drive is transmitted to thedriving bevel gear 6, which is rotated for pitch-change operation in anyconvenient manner.

The driven bevel I3 meshing with the driving bevel 6 is mounted on theairscrew blade root, the airscrew blade being indicated by the referencenumeral I4. Projecting internally from the bevel I3 is a bevel ringmounting plate I5, which is carried by a complementary mounting plate I6formed on the boss II (in dotted lines) which mounts the blade shank. Itwill be notedv that the mounting plates I5 and I6 are formed withcomplementary recesses or notches I8 and I9, respectively, into whichnotches spring packs 2U are inserted. The spring packs 20 are, in fact,laminated springs which are securely located in the complementaryrecesses I8 and I9, producing a tendency in the arrangement illustratedin Figure l to urge the mounting plate I5, and with it the bevel I3,leftwardly in relation tothe mounting plate I6, which is securely borneby the airscrew hub, it being understood that in this case thepitch-change driving bevel which cooperates with the driven bevel I3 onthe blade root is intended to be on the lefthand side. In this case thespring packs 2U can be presumed to be of the sort which are naturallystraight but which are assembled in a somewhat distorted condition, sothat the tendency is for them toy straighten.

It will be noted that though the mounting plate I6 is of somewhatirregular formation, a certain amount oi' clearance is provided allround its peripiiery between it and the complementary mounting plate I5;but it Will also be observed that diametrically-opposite drivingprojections 2| and Zz of the mounting plate I6 have their lateral edgesZIA and 22A accurately fitting cooperating edges of the recesses 23 and24 complementary to trie driving projections 2| and 22, respectively,

and iormed in the mounting plate I5. Thus, whereas the arrangement issuch that the spring packs zu tend to urge the mounting plate I5leitwai-aly with respect to the mounting plate I6, the driving torque istransmitted through the lateral edges oi' the cooperating projectionsand recesses 2|, 23 and 22, Z4, thus providing for resilient loading ofthe bevel I towards its cooperating pitchchange driving bevel (notsiiown) and at the same time a driving connection for effective rotationoi the blades Hi each about its pitch-change axis, with complete freedomfrom backlash.

Whereas the arrangement shown in Figure l may be a convenient, one inlarge airscrews where a fairly large diameter bevel can be accommodated,a situation may arise in smaller airscrews where the bevel diameter doesnot permit the mounting plates I5 and I6 to lie in the same plane. Tomeet such a case the arrangement shown in Figure 2 has been devised. Inthis case the spring 2 packs 25 extend longitudinally of the blademountings, the bevel mounting plate 26 being provided withupwardly-projecting dogs 21 which engage recesses 28 provided in themounting plate 29 secured to the blade roots. The dogs 21 engage theedges 28A of the recesses 28 so that they are capable of transmittingdriving torque with complete freedom from backlash; but on the contrarya clearancei30 is provided between the end of the recess and adjacentwall of the dog 21 so as to permit lateral movement under the influenceof the spring packs 25, which, as vwith the arrangement shown in Figure1, are secured in complementary recesses so as to extend under stresslin shear between the bevel mounting ring 26 and the mounting plate 29secured on the blade root.

It will be appreciated that in variable'pitch air-v screws rotation ofthe driven bevels mounted on the blade roots is only partial, and thusthere is no objection to the fact that the driven bevels illustrated inFigures 2 and 3 are resiliently loaded leftwardly in a sense parallel toa diameter passing through the torque transmitting connection(projections 2|, 22 and cooperating recesses 23, 24 in Figure 1 and dogs21 and cooperating recesses 28 in'Figure 2). l It is to'beunderstoodthat the spring packs 2li, 25 of Figures 1 and 2,respectively, instead of being in the form ofY laminated leaf springs,may comprise coil springs, rubber, or any'other suitable resilientmeans.

Although the foregoing description deals more particularly with theapplication of the invention to variable pitch airscrews, it may equallywell be applied to marine propellers in which provision is made forpitchY changing; and in fact to any arrangement of 'toothed-gearcoupling in which a driven member is but `partially rotatablewithrespect to its driving member.

vWhat We claim is:

`l; In pitch-change drive-transmitting gearing of a variable pitchairscrew, a driven bevel having abacklash free driving connection withan airscrew blade root for pitch-change drive-transmitting purposesthrough members permitting limited relative movement in a sense parallelto a diameter intersecting the arc of engagement between said drivenbevel and a-cooperatingpitchchange driving bevel,- and resilient meansoperating between said members resiliently-l'oading saidv driven beveltowards said driving bevel;

2. An arrangement as set forth in claim 1, in which the members whichpermit the relative movement under the influence off the resilientloading means are disposed one within the other.V

3. An arrangement as set forth in claim 1, in which the members whichpermit the relative movement under the influence of the resilientloading means are disposed in axially spaced relationship.

4. Gear mechanism for retaining two meshing gears in engagement,comprising a rotative member disposed generally concentrically with oneof such gears and spaced transversely of such members axis of rotationfrom the other of such gears, and resilient means engaging both saidrotatable member and the rst gear, and operable to urge the first geartoward the second gear in a direction transversely of said rotativemember.

, 5. The gear mechanism of claim 4, and guide means interengaged betweenthe rotative member and the first `gear guiding the same for relativemovement parallel to only one plane in which the axis of rotation of therotative member lies.

6. A mounting for a driven gear adapted to mesh with a drive gear,comprising a shaft mounted for rotation about an axis through less thana half-revolution and disposed substantially concentrically with thedriven gear, the driven gear and said shaft having cooperating abutmentsguiding such gear and shaft for relative movement transversely of saidshaft, and spring means interengaged between the driven gear and saidshaft urging movement of the driven gear relative to said shaft towardthe driving gear, while guided by said abutments.

7. A mounting for a driven gear adapted to mesh with a drive gear,comprising a shaft mounted for rotation about an axis through less thana half-revolution and disposed substantially concentrically with thedriven gear, the driven gear and said shaft having cooperating abutmentsguiding such gear and shaft for relative movement transversely of saidshaft, and a plurality of spring leaves interengaged lbetween the drivengearand said shaft urging movement of thev driven gear relative to saidshaft toward the driving gear, While guided by said abutments.

8. The mounting of claim 7, in which the spring leaves are ,disposedtransversely of the shaft.

9. The mounting of claim '7,-in which the spring leaves extend generallyparallel to the shaft.

10. The gearing mechanism of claim '7, in which the spring leaves arearranged in a plurality of packs, each composed of a plurality of springleaves disposed in face to face engagement, and each pack has one endengaged with the shaft and its other end engaged with the driven gear.

KENNETH BRYAN GILLMORE. ROBERT HENRY WARDE.

